1. Field of the Invention
Device for filtering polymer melts having a housing provided with an inflow as well as an outflow for the polymer melt in which a slide is seal-tight arranged between the openings of the inflow and the outflow so as to be moveable in a direction transverse to the inflow and the outflow, which slide has filter layers supported in cavities and correlatable with the inflow and outflow as desired.
2. Description of the Related Art
Such devices for filtering polymer melts, in which the filter layers contained in the filter cavities are movable, as desired, into the melt flow by displacement of the parallelepipedal or cylindrical slides, are known in various embodiments. The housing in which the slide is slidably arranged can be of a one-part construction or can be comprised of several mechanical component groups which are fixedly connected to one another, for example, by screws. In all of these arrangements, however, the sealing of the highly pressurized melt flow relative to the exterior is a problem, especially since the slides should be slidable as easily as possible and the sliding movement of the surfaces gliding on one another should exert only a minimal resistance against sliding despite the acting pressure.
In order to realize these problematic sealing configurations, it has been customary so far to provide very long sealing surfaces so that the melt will play itself out in the formed narrow gap, i.e., its pressure will decrease along this gap with minimal gradient. On the other hand, the parts to be sealed relative to one another have been manufactured in the past with very tight tolerances and high pressing forces have been exerted which require complex spring elements for their stabilization and which require with regard to the sealing rings a very high hardness as well as minimal frictional resistance and minimal erosion in order to be able to perform the required movement with acceptable expenditure. DE-A 17 29 396 suggests a complex arrangement which, when the sliding movement is started, relieves the seal and, after completion of an adjusting movement, realizes a high compression force by means of a wedge drive. Finally, it is also possible to employ minimal pressing forces when extremely high fitting tolerances and thus correspondingly high manufacturing expenditures are employed. In all of these cases, however, an undesirable high mechanical expenditure in combination with a limitation of the movability results.
FR 1 210 419 shows cylindrical components with outwardly projecting beads whose flanks are outwardly inclined and which are surrounded by two clamping ring halves that are moveable toward one another. A tube socket surrounding a perforated plate is provided as a seal. No measures are provided in the connecting area to move, remove or exchange parts so that no suggestions can be taken in regard to filter exchange arrangements.
The invention therefore has the object to provide a device of the aforementioned kind which is of a simple configuration, allows a relatively inexpensive manufacture by providing a relatively wide tolerance range and which furthermore makes it possible to move the slide, having the filter layers to be exchanged, with relatively minimal forces and without significant wear of the guiding and sealing surfaces.
This object is solved by the features listed in the characterizing portion of the claim 1. They make it possible to operate with relatively minimal pressing forces without losing effectiveness of the seals so that the required forces for movement as well as the wear resulting from the movement of the guide and sealing elements is minimal.
Expedient, advantageous, and inventive further developments of the subject-matter of the invention can be taken from the following dependent claims.